interface trouble - how do i fill my skill bar?

Don't beat me, but i'm a newbie, and i can't for the life of me figure out how to get a skill that i bought into my skill bar. I have tried various ways of dragging, shift-, alt- and ctrl-clicking, shiftclicking while holding a number key down, but haven't had any success so far. Browsed the forum for a bit, but didn't find anything yet. Any help?

Huh. I'm at work right now so i can't test it, but i'm a bit confused now. The skill bar, iirc. has 4 slots. Indeed some of the buyable skills are preassigned to those slots, so if i buy those, i can use them. But every DG has 10 or so skills. Some are not on the slots. I DID notice that some of them are passive, but are there only 4 active skills per DG? For example, when i was playing demon assassin, i bought some sort of healing skill (lower part of the page) and i don't think it was a passive skill, but it wasn't on the 4 slots either. But there's a possibility that i misread it.

Certain skills are passive, meaning you cannot activate them. Sedna's healing wind for example automatically grants health per second to every allied unit in range. Regulus' sniper scope ability increases his range, and there is nothing you need to do.

There are 8 "normal" demigods who have 4 activateable abilities. Using these abilities is relatively easy. Most require you to choose a target after clickng them (fireball, penitence, pounce) but some just go off like surge of faith or circle of flames or fire nova etc.

The other 2 have form switching, 3 abilities in mode 1, 3 more in mode 2

I see. So there is no need to define the skill bar. And the demon hunter is probably one of the form switchers, since he's not in the manual and was, i believe, added after i updated the game. Which could explain why i couldn't access that skill because maybe it was the wrong form (or maybe it WAS passive).